Idle Control Valve

[Paull]

Can anyone explain accurately what the ICV does, and whether it ceases to be functional at a certain Rev band.

I have stripped and cleaned my M today and have totally eradicated the hesitation... It's like a different car. Couldn't get it to kangaroo at all.

When I removed the ICV it didn't make a noise at all despite shaking, tilting and twisting it. I flushed it with carb cleaner and still no clicking, I left it for about ten minutes and it then seemed to free itself and clicked freely.

I know the hesitation has been widely discussed on these forums but I noticed that the TPS in linked to the ICV as is the MAF wiring I think, it also seems that the two pipes link the air box with a direct link behind the throttle butterfly's. Hopefully someone can explain this better and confirm if it is linked as previously mentioned.

I use my M very little only covered about 600 miles in the past 6 months, could the ICV be prone to sticking on under used Ms causing the hesitation.

If anyone is suffering from hesitation it may be worth removing the top pipe where it comes through the throttle bodies, spray a little cleaning fluid in and leave to evaporate and then see if the hesitation improves, may save undertaking a big strip.

 

[AndyBeech]

The ICV should be closed at any point above the normal idle speed I believe. Trying to remember when I tested it using INPA, I'm pretty sure it showed 'closed' almost as soon as pressing the throttle, although it could have been above 1000rpm.

In any case, if it's not functioning correctly, like it wasn't in your car, you effectively have a vacuum leak which would almost certainly have been causing your hesitation issues along with an unstable idle potentially. You should be able to flick it open and closed fairly easily with a solid 'clunk' and no stickiness in-between. Cleaning it should just be a case of a few cotton buds and a load of carb cleaner until it runs clear. You can then use the cotton buds to clean off the carbon deposits on the valve itself so it should look like new.

The MAF, TPS and ICV are all linked in various ways. The TPS position dictating when the ICV should be open or closed for example. The ICV takes it feed like you say from the bottom of the intake plenum which then leads to the metal tube above the throttle bodies and feeds air behind the butterfly's. It's all a bit confusing, but as you found it, it becomes a lot clearer when you have it all in pieces in front of you.

I would say it's worth most people at some point taking the intake side of things apart and giving it a good clean periodically. It's not that hard of a job and all you really need is a bit of carb cleaner, a few basic tools and some of the muffler clamps incase any break when you take it off. Cleaning down the whole intake side of things can be done in a morning if you know what your doing with it, doesn't have to be a big job. I've done it a few times now and can have it stripped down in less than an hour.